add Returns

base/abstractarray.jl

@@ -1810,7 +1810,7 @@ function hvcat(nbc::Integer, as...)
     mod(n,nbc) != 0 &&
         throw(ArgumentError("number of arrays $n is not a multiple of the requested number of block columns $nbc"))
     nbr = div(n,nbc)
-    hvcat(ntuple(i->nbc, nbr), as...)
+    hvcat(ntuple(Always(nbc), nbr), as...)
 end
 
 """
@@ -2112,7 +2112,7 @@ _sub2ind_vec(i) = ()
 
 function _ind2sub(inds::Union{DimsInteger{N},Indices{N}}, ind::AbstractVector{<:Integer}) where N
     M = length(ind)
-    t = ntuple(n->similar(ind),Val(N))
+    t = ntuple(Always(similar(ind)),Val(N))
     for (i,idx) in pairs(IndexLinear(), ind)
         sub = _ind2sub(inds, idx)
         for j = 1:N

base/dict.jl

@@ -797,7 +797,7 @@ function iterate(d::ImmutableDict{K,V}, t=d) where {K, V}
     !isdefined(t, :parent) && return nothing
     (Pair{K,V}(t.key, t.value), t.parent)
 end
-length(t::ImmutableDict) = count(x->true, t)
+length(t::ImmutableDict) = count(Always(true), t)
 isempty(t::ImmutableDict) = !isdefined(t, :parent)
 empty(::ImmutableDict, ::Type{K}, ::Type{V}) where {K, V} = ImmutableDict{K,V}()
 

base/exports.jl

@@ -21,6 +21,7 @@ export
     AbstractUnitRange,
     AbstractVector,
     AbstractVecOrMat,
+    Always,
     Array,
     AbstractMatch,
     AbstractPattern,

base/operators.jl

@@ -915,6 +915,38 @@ julia> [1:5;] |> x->x.^2 |> sum |> inv
 """
 |>(x, f) = f(x)
 
+# always
+"""
+    f = Always(value)
+
+Create a callable `f` such that `f(args...; kw...) === value` holds.
+
+# Examples
+
+```jldoctest
+julia> f = Always(42);
+
+julia> f(1)
+42
+
+julia> f("hello", x=32)
+42
+```
+
+!!! compat "Julia 1.7"
+    Always requires at least Julia 1.7.
+"""
+struct Always{V} <: Function
+    value::V
+end
+
+(obj::Always)(args...; kw...) = obj.value
+function show(io::IO, obj::Always)
+    show(io, Always)
+    print(io, "(")
+    show(io, obj.value)
+    print(io, ")")
+end
 # function composition
 
 """

test/arrayops.jl

@@ -1153,17 +1153,17 @@ end
     # issue #5177
 
     c = fill(1,2,3,4)
-    m1 = mapslices(x-> fill(1,2,3), c, dims=[1,2])
-    m2 = mapslices(x-> fill(1,2,4), c, dims=[1,3])
-    m3 = mapslices(x-> fill(1,3,4), c, dims=[2,3])
+    m1 = mapslices(Always(fill(1,2,3)), c, dims=[1,2])
+    m2 = mapslices(Always(fill(1,2,4)), c, dims=[1,3])
+    m3 = mapslices(Always(fill(1,3,4)), c, dims=[2,3])
     @test size(m1) == size(m2) == size(m3) == size(c)
 
-    n1 = mapslices(x-> fill(1,6), c, dims=[1,2])
-    n2 = mapslices(x-> fill(1,6), c, dims=[1,3])
-    n3 = mapslices(x-> fill(1,6), c, dims=[2,3])
-    n1a = mapslices(x-> fill(1,1,6), c, dims=[1,2])
-    n2a = mapslices(x-> fill(1,1,6), c, dims=[1,3])
-    n3a = mapslices(x-> fill(1,1,6), c, dims=[2,3])
+    n1 =  mapslices(Always(fill(1,6)  ), c, dims=[1,2])
+    n2 =  mapslices(Always(fill(1,6)  ), c, dims=[1,3])
+    n3 =  mapslices(Always(fill(1,6)  ), c, dims=[2,3])
+    n1a = mapslices(Always(fill(1,1,6)), c, dims=[1,2])
+    n2a = mapslices(Always(fill(1,1,6)), c, dims=[1,3])
+    n3a = mapslices(Always(fill(1,1,6)), c, dims=[2,3])
     @test size(n1a) == (1,6,4) && size(n2a) == (1,3,6)  && size(n3a) == (2,1,6)
     @test size(n1) == (6,1,4) && size(n2) == (6,3,1)  && size(n3) == (2,6,1)
 

test/iterators.jl

@@ -198,7 +198,7 @@ end
     @test collect(takewhile(<(4),1:10)) == [1,2,3]
     @test collect(takewhile(<(4),Iterators.countfrom(1))) == [1,2,3]
     @test collect(takewhile(<(4),5:10)) == []
-    @test collect(takewhile(_->true,5:10)) == 5:10
+    @test collect(takewhile(Always(true),5:10)) == 5:10
     @test collect(takewhile(isodd,[1,1,2,3])) == [1,1]
     @test collect(takewhile(<(2), takewhile(<(3), [1,1,2,3]))) == [1,1]
 end
@@ -209,8 +209,8 @@ end
     @test collect(dropwhile(<(4), 1:10)) == 4:10
     @test collect(dropwhile(<(4), 1:10)) isa Vector{Int}
     @test isempty(dropwhile(<(4), []))
-    @test collect(dropwhile(_->false,1:3)) == 1:3
-    @test isempty(dropwhile(_->true, 1:3))
+    @test collect(dropwhile(Always(false),1:3)) == 1:3
+    @test isempty(dropwhile(Always(true), 1:3))
     @test collect(dropwhile(isodd,[1,1,2,3])) == [2,3]
     @test collect(dropwhile(iseven,dropwhile(isodd,[1,1,2,3]))) == [3]
 end

test/operators.jl

@@ -279,3 +279,13 @@ a = rand(3, 3)
 @test transpose(a) === a'ᵀ
 
 @test [Base.afoldl(+, 1:i...) for i = 1:40] == [i * (i + 1) ÷ 2 for i = 1:40]
+
+@testset "Always" begin
+    @test @inferred(Always(1)()   ) === 1
+    @test @inferred(Always(1)(23) ) === 1
+    @test @inferred(Always("a")(2,3)) == "a"
+    @test @inferred(Always(1)(x=1, y=2)) === 1
+    val = [1,2,3]
+    @test Always(val)(1) === val
+    @test sprint(show, Always(1)) == "Always(1)"
+end